1. Field of the Invention
The present invention relates to polymer blends, to methods of blending, to articles made from the blends, and to methods of making articles. In another aspect, the present invention relates to polymer blends of elastomers, syndiotactic polypropylene and block copolymers, to methods of blending elastomers, syndiotactic polypropylene and block copolymers, to articles made from blends of elastomers, syndiotactic polypropylene and block copolymers, and to methods of making articles from blends of elastomers, syndiotactic polypropylene and block copolymers.
2. Description of the Related Art
Present blend compositions for mechanical rubber goods (MRG) applications utilize blends of elastomers, crystalline polystyrene polymers and styrene-butadiene-styrene block copolymers.
U.S. Pat. No. 4,041,103, issued Aug. 9, 1977 to Davison et al., discloses blends of a block copolymer and a polyamide. Styrene-butadiene-styrene copolymer is listed is as an example of a block copolymer which can be utilized. The '103 patent teaches that best results are obtained when the viscosities of the block copolymer and polyamide are substantially the same at the conditions of temperature and shear used for blending and processing. The '103 patent further teaches that additional resins may be employed in matching viscosities, with isotactic and atactic polypropylenes disclosed as being suitable for use in matching viscosities.
U.S. Pat. No. 4,386,187, issued May 31, 1983 to Grancio et al., discloses a thermoformable polymer blend composition comprising a styrene polymer, a crystalline olefin polymer such as polypropylene, and a block copolymer such as styrene-butadiene-styrene copolymer which acts as a compatibilizer for the olefin and styrene polymers in the blend. The composition may optionally include copolymers of monoolefins with other monoolefins.
U.S. Pat. No. 4,489,034, issued Dec. 18, 1984 to Davison, discloses a thermoforming process using a modified polymer blend. The polymer blend of polyethylene and crystalline isotactic polypropylene is modified by, for example, ethylene/propylene rubber, with the modifier present in the range of about 5 to about 35 weight percent.
U.S. Pat. No. 4,838,939, issued Jun. 13, 1989 to Kanda et al., discloses polymer compositions which are useful in damping sheets for motor vehicles. The composition is discloses as including an organic fibrous filler and a binder component. Examples of the binder component include, rubbers such as styrene butadiene rubber, and synthetic resins such as polypropylene.
U.S. Pat. No. 5,256,226, issued Oct. 26, 1993 to Marzola et al., discloses an adhesive polymer composition for repairing exposed or damaged parts of a plastic coating on metal tubing. The adhesive polymer composition is disclosed as including isotactic polypropylene and styrene-butadiene-styrene block copolymers.
U.S. Pat. No. 5,380,796, issued Jan. 10, 1995 to Campbell et al., discloses compositions of polyphenylene ethers and functionalized olefin polymers such as polyethylene. The composition can include impact modifiers, such as styrene-butadiene-styrene copolymers.
European Patent Application 0 060 524 A2, published Sep. 22, 1982, discloses a thermoplastic rubber consisting of a mixture of polypropylene, high-impact polystyrene and a styrene/diene block copolymer. The polypropylene is an isotactic polypropylene described as having an "isotacticity index of at least 80". The amount of elastomeric styrene/diene block copolymer is disclosed as being between 30 and 90 weight percent.
"Performance/Microstructure Relationship Of Blends Of Asphalts With Two Incompatible Polymers", C. Lenoble, Fuel Science and Technology Int'l, 10(4-6), 549-564 (1992), discloses an asphalt composition also containing an atactic polypropylene and a styrene-butadiene-styrene triblock copolymer. The composition was made by first mixing styrene-butadiene-styrene into asphalt, and then adding atactic polypropylene into the mixture. The atactic polypropylene and the styrene-butadiene-styrene triblock copolymer were observed as being segregated within the asphalt.
"Current Applications Of Styrene Block Copolymer Rubbers", G. Holden, Journal of Elastomers and Plastics, Vol. 14, page 148-154 (July 1982), discloses blends of styrene-butadiene-styrene polymers with polystyrene, polyethylene or polypropylene show improved impact and tear resistance with minimum changes in tensile strength and flexural modulus.
However, in spite of these advancements in the prior art, there is still a need for an improved elastomer, styrene-butadiene-styrene and polypropylene blend composition for use in mechanical rubber goods applications.
This and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.